ENThe article analyses how the sexual education and other expert sexological/psychiatric/forensic texts produced in late socialist Lithuanian SSR promoted ideas of gender complementarity and difference and how these ideas were intertwined with homophobic rhetoric. In line with similar developments both East and West of the Iron Curtain in the same period, the experts warned about the dangers of homosexuality and argued that the proper gender roles are declining in a modern society, but have to be protected for the sake of marital happiness and healthy society. While focusing on the particular context of the Western borderlands of the Soviet Union, the article pays attention to the transnational knowledge flows and demonstrates the connections between eugenic, social constructionist and other modern theories as they got taken up in socialist discourses of gender and sexuality. Keywords: homosexuality, Soviet Union, sexual science, Lithuania, gender complementarity, homophobia.